At Sāvatthi.

"Bhikkhus, a bhikkhu should live with mindfulness and with full awareness. This is my instruction to you.

And how, bhikkhus, is a bhikkhu mindful? Here, bhikkhus, a bhikkhu dwells observing the body in and of itself, with continuous effort, with full awareness, and being present, having removed craving and displeasure with regard to the world; Similarly, he dwells observing feelings in and of themselves, mind in and of itself, and mental qualities in and of themselves, with continuous effort, with full awareness, and being present, having removed craving and displeasure with regard to the world. It is in this manner, bhikkhus, that a bhikkhu is mindful.

And how, bhikkhus, is a bhikkhu fully aware? Here, bhikkhus, for a bhikkhu, feelings arise, remain, and disappear with full awareness. Thoughts arise, remain, and disappear with full awareness. Perceptions arise, remain, and disappear with full awareness. Thus, bhikkhus, a bhikkhu is with full awareness. Bhikkhus, a bhikkhu should live mindfully and with full awareness. This is my instruction to you."